Free At Last, Free At Last
Engineers and mission managers for NASA's Mars Exploration Rover
mission cheered when images from the Martian surface confirmed
Opportunity had successfully escaped from a sand trap.
From about 174 million kilometers away (about 108 million
miles), the rover team at NASA's Jet Propulsion Laboratory,
Pasadena, CA, had worked diligently for nearly five weeks to
extricate the rover. The long-distance roadside assistance was a
painstaking operation to free all six wheels of the rover, which
were mired up to their rims in the soft sand of a small martian
dune.
"After a nerve-wracking month of hard work, the rover team is
both elated and relieved to finally see our wheels sitting on top
of the sand instead of half buried in it," said Jeffrey
Biesiadecki, a JPL rover mobility engineer.
Traction was difficult in the ripple-shaped dune of windblown
dust and sand that Opportunity drove into on April 26. In the weeks
following, the rover churned 192 meters (629 feet) worth of wheel
rotations before gaining enough traction to actually move one meter
(about three feet). The rover team directed the drives in cautious
increments from May 13 through June 4.
"We did careful testing for how to get Opportunity out of the
sand. Then we patiently followed the strategy developed from the
testing, monitoring every step of the way," Biesiadecki said. "We
hope to have Opportunity busy with a full schedule of scientific
exploration again shortly.”
Opportunity's next task is to examine the site to provide a
better understanding of what makes that ripple different from the
dozens of similar ones the rover easily crossed. "After we analyze
this area, we'll be able to plan safer driving in the terrain
ahead," said JPL's Jim Erickson, rover project manager.
Both Spirit and Opportunity have worked in harsh martian
conditions much longer than anticipated. They have been studying
geology on opposite sides of Mars for more than a year of extended
missions since successfully completing their three-month primary
missions in April 2004.
"The first thing we're going to do is simply take a hard look at
the stuff we were stuck in," said Dr. Steve Squyres of Cornell
University, Ithaca, N.Y. He is the principal investigator for the
Mars rovers' science instruments. "After that, we will begin a
cautious set of moves to get us on our way southward again. South
is where we think the best science is, so that's still where we
want to go.”
Shortly after landing in January 2004, Opportunity found layered
bedrock that bore geological evidence for a shallow ancient sea.
Spirit did not find extensive layered bedrock until more than a
year later, after driving more than two miles and climbing into a
range of hills known as "Columbia Hills."